There have been ad hoc network systems that include a plurality of nodes communicating with gateways (GWs) that are specific nodes serving as windows for external servers. In the ad hoc network system, the respective nodes form communication routes by relaying packets received from the adjacent nodes to other nodes.
A conventional technique is described that forms the communication routes of the packets. In the conventional technique, respective nodes calculate evaluation values of the multiple communication routes to a specific node such as a GW using evaluation parameters such as the number of hops of the packets and reception levels. The respective nodes then select the communication routes to the specific node on the basis of the respective calculated evaluation values. A conventional technology is described in Japanese Laid-open Patent Publication No. 2011-223394, for example.
The conventional technique, however, has a problem in that when the ad hoc network system is applied to a tree structure with a GW as the root, a traffic load may be concentrated on an aggregate section located on an upstream side in the tree structure.